Process and apparatus for the gasifica-
tion of ash-containing fuel



m US A E M K I2 c m 0 Mn May 30, 1967 PROCESS AND APPARATUS FOR THE GASIFICATION INVENTOR R G. Coc/rerham United Stats Patent C 3,322,521 PROCESS AND APPARATUS FOR THE GASIFICA- THEN 6F ASH-CONTAINER FUEL Robert George Cockerharn, Solihull, England, assignor to The Gas Council, London, England, a statutory 3,322,521 Patented May 30, 1967 cles of the carbonaceous portion. As the gasification proceeds the quantity of the denser ash portion increases at the expense of the less dense carbonaceous portion.

The following experiments illustrate the phenomenon described above. Two coals A and B were each gasified in British Fcorpioiationzs 1963 S N 291 510 the form of a fluidised bed with steam and an at a temperature of 700 C. Each coal had a particle size ranging Clalms Pnomy, g g gg Bmam July 1962 from 100 microns up to 400 microns. These coals had 15 Claims. (Cl. the followmg percentage compositions by weight. This invention relates to the gasification of particulate 0021A C oalB solid ash-containing carbonaceous fuel, for example, coal or coke, n the fluidised state. The term gasificat on 1s Moisture content 7. 5 129 used herein to denote any reaction between a Solid car- Volatile matter 32.9 36.6 bonaceous fuel and a reactive gas (which includes a mixf" i g? ture of gases), which results in the conversion of the carbonaceous constituents of the fuel into a gaseous prodnot (which includes a mixture of such products), for ex- Coal A was obtained from the Birch Coppice mine and ample, the reaction of a carbonaceous fuel with steam and coal B was obtained from the Desford mine. a gas comprising oxygen, such as air or oxygen alone, to Each coal was progressively gasified in a reactor in form hydrogen and carbon monoxide, or with hydrogen stages for various periods, coal A being gasified in six to form methane. stages and coal B in three stages. After each stage, the

In carrying out such reactions the gas is passed upmaterial of the fluidised bed was removed from the rewardly through a bed of the particulate carbonaceous actor, and, when cold, was wholly fluidised by passing a fuel so as to maintain the latter in the fluidised state. For current of cold air upwardly through it. The velocity of economic reasons it is necessary that these reactions should the air was then gradually decreased to a value at which be carried out in a continuous manner by continuously or the particles of the ash portion collected at the bottom of intermittently supplying fresh carbonaceous fuel to the the reactor, and the particles of the carbonaceous portion fludised bed, and the removal of ash from the bed presents remained in the fluidised state. The carbonaceous portion a problem. Usually, the ash content of the bed is prevented and the ash portion, thus separated from each other, were from becoming undesirably high by continuously or intereach weighed, and a small amount of each portion was rnittently withdrawing a part of the'fluidised material withdrawn to determine the ash content. The carbonafrom the bed. As, however, the ash content of the maceous and ash portions were then mixed together and reterial withdrawn is substantially the same as the average turned to the reactor for the next stage of gasification. ash content of all the materials in the bed, a considerable The results are given in the following table:

Carbonaceous portion Ash portion Total Ash content, percent by Percent by Ash content, Percent by Ash content, Weight of weight of percent by weight of percent by bed material bed weight bed weight of portion Coal A 36. 1 75.8 20. 0 24. 2 86. 5 47. 4 61. 2 21.4 38.8 90. 6 57. 7 54. 6 22. 6 45. 4 86. 3 64. 3 40. 7 28. 9 59. a 88. 5 76. 5 32.8 34. 4 67. 2 87. 0 84.3 8.4 28.6 91.6 87.8

Average bulk density 35 lbs. per cubic foot 76 lbs. per cubic it.

Coal B 30.6 69. 4 19. 4 30. 6 56.9 51. 3 51.1 22. 5 48. 9 81. 9 64. 6 30. 1 21. 0 69. 9 79. 7

Average bulk density 34.5 lbs. per cubic ft. 65 lbs. per cubic ft.

proportion of unre-acted carbonaceous material is present in the material withdrawn.

The present invention is based on the observation that the particles of a fluidised bed of solid carbonaceous fuel, for example, coal, after it has undergone partial gasification, consist substantially of a mixture of two kinds of particles, one kind consisting predominantly of carbonaceous material, and hereinafter referred to as the carbonaceous portion of the bed material, and the other kind consisting predominantly of ash, and hereinafter referred to as the ash portion of the bed material. Due to this dilference in composition, these two kinds of particles have substantially difierent average densities, the average density of the particles of the ash portion being substantially higher than the average density of the parti- The bulk density was determined in the settled state, that is to say, such as results from pouring the powder into a receiver without causing further settling, for example, by agitating the receiver.

From the above experiments, it will be understood that an intimate mixture of particles of the aforesaid two kinds can be maintained in the fluidised state if the fluidising gas has a sufficiently high velocity, and that the velocity can be reduced to a value at which the particles of the ash portion separate out below the bed, and particles of the carbonaceous portion remain fluidised.

The present invention provides a process for the gasification of particulate solid ash-containing carbonaceous fuel in a fluidised state in a continuous manner, which comprises feeding the particulate fuel to and reacting it with 3 a a reactive gas in a bed of particulate material that con- Moisture content 6.3 sists substantially of a carbonaceous portion and an ash Volatile matter 27.4 portion resulting from reaction of the fuel with the Fixed carbon 33.3 gas, passing a gas comprising the reactive gas upwardly Ash through the bed at a velocity such as t0 maintain the bed The results are given in the following table:

Ash content of bed material Coal A, 64.3 Coal B, 64.6 Goal 0, 55.6

Carbon- Ash Carbon- Ash Carbon- Ash aceous portion aceous portion aceous portion portion portion portion Average particle size in microns 145 190 157 188 140 203 Bulk density, lbs/cu. it 36. 2 76.6 33. 2 65. 6 40. 0 66. 8

Velocity for separation, inches per seeond 1.8-2. 2 1.4-1.8 1. 2-1.

in the fluidised state, passing a gas upwardly through a separating zone below the fluidised bed at a velocity insutficient to fiuidise the particles constituting the ash portion but sufficient to fluidise the particles constituting the carbonaceous portion, and discharging from a collecting zone the particles of the ash portion that fall through the separating zone.

The gas that is passed upwardly through the separating zone at a velocity such as to cause separation of particles of the ash portion from particles of the carbonaceous portion may be an inert gas, but it is usually preferable to use a part of the reactive gas. When the reactive gas consists of a mixture of gases, the said part may be at least a part of one of the components of that mixture.

The process is advantageously carried out in a reaction vessel having, below the region of the fluidised bed, two gas inlet means arranged one above the other from at least one of which the reactive gas is supplied, the gas, that is passed upwardly at a velocity such as to for-m below the fluidised bed the separating zone in which particles of the ash portion cease to be fluidised and so fall into the collecting zone, being supplied from the lower gas inlet means. The control of the velocity of the gas for the latter purpose depends on various factors, such as the quantity of gas supplied through the inlet means in unit time and the cross-sectional area of the passage through which it is passed. It is also possible to impart to the gas a gradually increasing velocity between lower and upper limits of velocity that include the velocity required to bring about the separation. For this purpose the cross-sectional area of the passage through which the gas passes may gradually decrease and/ or the temperature of the gas may gradually increase so that its velocity increases due to thermal expansion. Since it is usual in gasification processes to introduce the gas at a temperature below the reaction temperature, it will generally be convenient in the process of the invention to form the separating zone by arranging that the gas issuing from the lower inlet means will be subjected by contact with the hot particulate material to a gradually increasing temperature such that the velocity of the gas increases through a range that includes the velocity required to bring about the separation.

The velocity required to bring about separation of the ash portion varies depending on the average particle size of the particles of the bed, and on the densities of the particles of the ash portion and of the carbonaceous portion, which densities, especially in the case of the ash portion, will depend on the character of the mineral matter present in the carbonaceous fuel used. In general the velocity is within the range of from 0.5 to 4.0 inches per second for most particle sizes used and densities found in practice. The results of experiments with the coals A and B referred to above and with another coal C, will serve to illustrate suitable velocities for separation. Each of these coals had a particle size ranging from 100 microns to 400 microns. Coal C had the following percentage composition by weight, and was obtained from the Coppice (Cannock) mine.

The gasification of carbonaceous fuel with steam and a gas comprising oxygen, preferably steam and oxygen alone, may be carried out under the known conditions for this reaction. There is advantageously used a temperature within the range of from 800 C. to 1300" C. The process may be carried out under atmospheric pressure or superatmospheric pressure depending on the usual considerations. When oxygen alone is used the ratio of steam to oxygen is usually about 2:1 parts by volume.

For the hydrogenation of carbonaceous fuel with hydrogen to form methane there is used a gas consisting mainly of hydrogen, for example, hydrogen alone or a gas containing carbon monoxide and hydrogen, the proportion of the latter being at least 50 percent by volume. The temperature is advantageously within the range of from 700 C. to 1200 C., preferably 800 C. to 950 C. The pressure is at least 5 atmospheres gauge and advantageously about 50 atmospheres gauge.

There is a tendency for the ash portion alone to sinter under some conditions, for example at temperatures within the range of from 1000 C. to 1300 C., or at temperatures as low as 800 C., due to the nature of the ash present in some carbonaceous fuels, and especially when the reactive gas has reducing properties that lower the fusion point of the ash, for example, by reducing ferric iron therein to the ferrous state. However, owing to the good intermixing of the particles of the ash and carbonaceous portions that takes place during fiuidisation, sintering of the bed does not occur at temperatures at which the ash portion alone would sinter.

It is an important advantage of the process of the in vention that, when the gasification temperature is above the sintering temperature of the ash portion alone, the particles of the ash portion as they fall through the separating zone can be cooled to a temperature below the sintering temperature. This cooling may be effected by introducing into the separating zone at a temperature below the sintering temperature the gas that is passed upwardly through the said zone. The gas that is introduced through the lower inlet means at a temperature below the gasification temperature and becomes heated by contact with the hot particulate material to form the separating zone, as described above, may have a temperature below the sintering temperature of the ash portion, so as to bring about the aforesaid cooling.

With some gasification processes that involve highly exothermic reactions it may be difficult to achieve adequate control of temperature in a normal fluidised bed. This is the case, for example, in carrying out the gasification with steam and oxygen alone, owing to the highly exothermic character of the reaction between the carbonaceous material and oxygen, and in spite of the moderating effect of the reaction between the carbonaceous material and steam. It may, therefore, be of advantage to carry out such gasification processes in a bed of the particulate material in which the fluidised material is caused to circulate so as to cause a more uniform temperature distribution. For this purpose there may be used a reaction vessel in the lower part of which are located the upper and lower gas inlet means, and in the upper part of which the particulate material is maintained by the gas in the form of a fluidised bed in which circulation of the suspended material is caused by the difference in density between a zone of descending fluidised particles and a zone of ascending particles being entrained by the gas. The zone of ascending entrained particles may be formed by providing within the reaction vessel above the upper inlet means an upwardly extending passage located below and communicating with the region of the fluidised bed and having an internal cross-sectional area such as to impart to the gas flowing upwardly therethrough from the gas inlet means a velocity such as to cause entrainment of the particles, and the zone of descending fluidised particles may be formed by a downcomer passage communicating at its upper end with the region of the fluidised bed and at its lower end with the lower end of the said upwardly extending passage, the cross-sectional area of the downcomer passage being such as to ensure the maintenance of fluidisation of particles descending therein.

The downcomer passage may be a single passage or it may be subdivided into two or more passages. Advantageously, the said upwardly extending passage is provided within a vertical open-ended tubular member of which the outer surface is spaced from the inner surface of the reaction vessel to form between these surfaces an annular downcomer passage, of which the cross-sectional area is such as to ensure the maintenance of fluidisation of particles descending therein.

Methods of carrying out the process of the invention will now be described with reference to the accompanying drawings, in which:

FIGURE 1 shows in vertical section a reaction vessel for use with a normal fluidised bed, and

FIGURE 2 shows in vertical section a reaction vessel for use with a fluidised bed in which the suspended material is caused to circulate.

Referring to FIGURE 1, the reaction vessel comprises an elongated cylindrical chamber 1 having at its lower end an upper gas distributor 2, through which the reactive gas is supplied, and above which the particulate carbonaceous material is maintained in the form of a fluidised bed. A lower gas distributor 3 serves for the introduction of the gas that is to form, between the upper and lower inlet means, a zone in which the ash portion is separated from the carbonaceous portion. As shown in the drawing, the distributor 2 is formed by a plurality (three as shown) of concentric circular tubes 4 pierced with orifices in their upper surfaces. Gas is supplied to the tubes from a conduit 5 that leads to a distributing conduit 6, with which each tube communicates through connections located at the ends of a diameter of each tube. As shown in the drawing, the distributor 3 is of the same construction as the distributor 2. The construction of the distributors shown is such as to enable the particles and gas to move past the distributors with little obstruction. Other constructions to fulfil the same purpose may be used.

The vessel is also provided with a dip leg 7 for feeding the particulate fuel to the fluidised bed, and an outlet conduit 8 for the gas produced. The lower end of the reaction chamber is formed as an ash-collecting chamber 9, of which the floor is of conical shape to ensure satisfactory discharge of the ash through an ash discharge outlet 10 having a valve 10a.

For gasification with steam and oxygen alone it is preferable to supply steam and oxygen through the upper distributor, the mixture being supplied in a quantity sufiicient to produce in the region above the distributor a gas velocity suflicient to maintain satisfactory fluidisation of the bed. A mixture of steam and oxygen ofthe same composition as that supplied to the upper distributor may be supplied to the lower distributor, but it is preferable to supply to the lower distributor steam alone or steam contain a small proportion of oxygen. The quantity of the gas supplied to the lower distributor to form the separating zone will be considerably smaller than the quantity of gas supplied to the upper distributor to maintain fluidisation. In FIGURE 1, the lower part of the vessel, in which the separating zone is formed, is shown as having an internal cross-sectional area smaller than that of the region of fluidisation above the upper distributor. This narrowing of the lower portion will be necessary when the quantity of gas supplied throughthe lower distributor is so small that its velocity would not reach a velocity suitable for separation, if the lower portion had the same diameter as the upper portion of the vessel.

The gas is supplied to the lower distributor at a temperature below the reaction temperature, and the velocity of the gas issuing therefrom gradually increases as it flows upwardly due to thermal expansion caused by contact with the hot particulate material, and the conditions are so adjusted that at some position between the upper and lower distributors the gas velocity is such as to cause separation of the ash portion. The ash portion falls to the bottom of the reaction vessel, and is discharged continuously or intermittently through the outlet 10, the rate of discharge being sufiicient to prevent an undesirable build up of ash in the lower part of the chamber 1.

In carrying out the hydrogenation of a carbonaceous fuel the hydrogen-containing gas may be supplied through both of the distributors 2 and 3, the quantity of gas supplied to the distributor 2 being such as to maintain fluidisation and the quantity supplied to the distributor 3 being such as to form a separating zone between the two distributors.

A method of carrying out the gasification with steam and oxygen while circulating the suspended material is exemplified with reference to FIGURE 2. In this figure the reaction vessel comprises an elongated cylindrical reaction chamber 11 within which is arranged a coaxial cylinder 12 open at its upper and lower ends. The cylinder 12 is arranged so as to provide an annular space forming a downcomer passage 13 between the outer surface of the cylinder and the inner surface of the reaction chamber. The inner surface of the cylinder 2 is provided with a thick lining 14', which reduces the internal diameter of the space within the cylinder to form a narrow axial passage 15. An inlet conduit 16 is provided for the supply of oxygen, and has at its end an opening through which the gas is directed upwardly into the passage 15. At the lower end of the reaction chamber 11 and below the cylinder 12 and the inlet conduit 16 is arranged a distributor 17, which communicates with a conduit 18 for the supply of steam to the space within the reaction chamber above the distributor.

The distributor 17 is shown as being of the same construction as the distributors shown in FIGURE 1, but, as stated in connection with that figure, it may be of another construction such as to offer little obstruction to the movement of particles and gas past the distributor.

It is convenient, but not essential, to supply the oxygen through the inlet 16 and the steam through the distributor 17 as described above. Thus, a mixture of steam and oxygen may be supplied through the inlet and the distributor, although it is preferable to supply most of the steam through the distributor.

The wall of the reaction chamber 11 in the region below the distributor 17 forms a conical collecting chamber 19 at the base of which is provided an ash discharge outlet 20 having a valve 21. The ash is discharged continuously or intermittently through the outlet 20. The reaction chamber 11 is also provided with an outlet conduit 22 for the gas produced, and a dip leg 23 for feeding the particulate fuel to the fluidised bed above the upper end of the cylinder 12.

During continuous operation the particulate material comprising a mixture of particles of a carbonaceous portion and particles of an ash portion is maintained in suspension by the gases supplied through the inlet conduit 16 and the distributor 17. In the region enclosed by the upper end of the cylinder 12 and by the wall of the reaction chamber above the cylinder, the material is maintained in the form of a fluidised bed, of which the upper level lies between the levels of the conduit 22 and of the opening of the dip leg 23. Material from the fluidised bed continuously flows down the annular downcomer passage 13 in the fluidised state, and passes from the lower end of this passage into the lower end of the cylinder 12, where it is carried upwardly by the gas into the narrow passage 15, in which particles are entrained with the gas ascending in the passage and returned to the fluidisedbed. As hereinbefore described, this circulation of the suspended material is caused by the diiference in density between the zone of ascending entrained particles in the passage 15 and the zone of fluidised particles descending in the downcomer passage 13.

The steam is supplied through the distributor 17 at a temperature below the reaction temperature, and the rate at which the steam is supplied is such that, due to thermal expansion of the steam resulting from contact with the hot particulate material, there is in the region above the distributor 17 and below the lower end of the cylinder 12 a zone in which the velocity of the steam reaches a value such as to cause the separation of particles of the ash portion from particles of the carbonaceous portion. In and below this zone the particles of the ash portion fall and are collected in the chamber 19. Above this zone the velocity of the steam is suthcient to fluidise the particles of the ash portion and of the carbonaceous portion.

The following example illustrates the gasiflcation process as carried out in a reaction vessel constructed as shown in FIGURE 2. The gas volumes are given in cubic feet as measured at 60 F. under 30 inches pressure of mercury, and, when applicable, as being saturated with water vapour at this temperature and pressure.

The dimensions of the various parts of the reaction vessel were as follows:

Internal diameter of the reaction chamber 11 ft 2.65 Internal diameter of the narrow passage 15 in 4 Length of the narrow passage 15 ft 9 Distance from the upper end of the passage 15 to the upper end of the cylinder 12 do 6 Length of the cylinder 12 do 21 Depth of the bed above the upper end of the cylinder do 8 Cross-sectional area of the downcomer passage 13 sq. ft 1.14

Coal A (referred to above) having a particle size ranging from 50 microns up to 400 microns was supplied to the reaction chamber 11 through the dip leg 23 at the rate of 4890 pounds per hour. Steam was introduced at 400 C. through the distributor 17 at the rate of 30200 cubic feet per hour, and oxygen was introduced at room temperature through the inlet 16 at the rate of 14600 cubic feet per hour. The pressure in the reaction vessel during the reaction was 300 pounds per square inch. The temperature of the suspension leaving the upper end of the passage 15 was 1040 C., the temperature within the fluidised bed above the upper end of the cylinder 12 was 1000 C., and the temperature of the particles leaving the lower end of the downcomer passage 13 was also 1000 C. Thus, the temperature of the ash portion of the suspended material was about 1000 C. as it entered the separating zone. This zone was formed a short distance above the distributor 17 at a level at which the velocity of the steam reached about 2 inches per second. Owing to the transfer of heat from the ash portion to the steam, the temperature of the ash portion which collected in the Percent Carbon monoxide 43 Hydrogen 25 Methane 13 Carbon dioxide 7 Water vapour 12 After condensing the water vapour present in the gas, there were obtained 2,040,000 cubic feet per day of a final gas (saturated with water vapour at 60 F. and 30 inches pressure of mercury) having the following percentage composition by volume:

Percent Carbon monoxide 50 Hydrogen 28 Methane 14 Carbon dioxide 8 The ash portion was removed from the chamber 19 through the discharge outlet 20 at the rate of 885 pounds per hour.

In order to start up the continuous process described above, a charge of coal particles was introduced into the reaction vessel and fluidised by means of air supplied to the vessel through the distributor 17. The bed of suspended particulate material was then heated to the required reaction temperature by burning a liquid or gaseous fuel supplied to the chamber through an inlet (not shown in the drawing) situated in or close to the inlet conduit 16. Then, when the cOal particles had reached the necessary temperature, the air was gradually replaced by the steam to be fed through the distributor 17, oxygen was introduced through the inlet conduit 16, and the feed of fuel to the burner was gradually reduced until all the heat was supplied by the reaction.

The coal particles may be fed through the dip leg 23 by pneumatic means, for example, by compressing a portion of the gas roduced to a pressure higher than the operating pressure within the vessel and injecting the coal particles in suspension in that gas.

I claim:

1. A process for the gasification of particulate solid ash-containing carbonaceous fuel in a fluidised state in a continuous manner, which comprises feeding the particulate fuel into and reacting it with a reactive gas in a bed of particulate material that consists substantially of a carbonaceous portion and an ash portion resulting from reaction of the fuel with the gas, passing a gas comprising the reactive gas upwardly through the bed at a velocity such as to maintain the bed in the fluidised state, passing a gas upwardly through a separating zone below the fluidised bed at a velocity insufficient to fluidise the particles constituting the ash portion but suflicient to fluidise the particles constituting the carbonaceous portion, and discharging from a collecting zone the particles of the ash portion that fall through the separating zone.

2. A process as claimed in claim 1, wherein the particulate material of the fluidised bed is caused to circulate from and back to the said bed above the separating zone by the difference in density between a zone of fluidised particles descending from the said bed and a zone of particles entrained by a part of the gas comprising the reactive gas so as to ascend to the fluidised bed.

3. A process as claimed in claim2, wherein there is used a reaction vessel having in its upper part the fluidised bed and in its lower part two gas inlet means, one located above and the other below the separating zone, and an p i er passage and a downcomer passage each located above both of said gas inlet means and each of said passages being in communication at its upper end with the said bed and at its lower end with the lower end of the other of the said passages, and wherein the reactive gas is supplied from at least one of the said gas inletmeans,

' the gas that is passed upwardlythrough the separating zone is supplied from the lower gas inlet means, particles are caused to descend from the said bed through the downcomer passage of which the cross-sectional area ensures that the descending particles are maintained in the fluidised state by upwardly flowing gas, and particles reaching the lower end of the said passage are caused to ascend to the said bed through the upriser passage of which the cross-sectional area ensures that the particles are entrained by gas flowing upwardly therein.

4. A process as claimed in claim 1, wherein the gas that is passed upwardly through the separating zone is a part of the reactive gas.

5. A process as claimed in claim 1, wherein the velocity of the gas in the separating zone is within the range of from 0.5 to 4.0 inches per second.

6. A process as claimed in claim 1, wherein the gasification temperature is above the sintering temperature of the ash portion alone, and the particles of the ash portion as they fall through the separating zone are cooled to below the sintering temperature by introducing into the separating zone at a temperature below the sintering temperature the gas that is passed upwardly through the said zone.

7. A process as claimed in claim 1, wherein the gas that is passed upwardly through the separating zone is given a gradually increasing velocity within said separating zone between lower and upper limits of velocity that include the velocity required to bring about the separation of particles of the ash portion by passing the said gas upwardly at a gradually increasing temperature so that its velocity increases due to thermal expansion.

8. A process as claimed in claim 7, which is carried out by contact of the upwardly flowing gas with the hot particles of the ash portion that fall through the separating zone.

9. A process as claimed in claim 1, wherein the reactive gas is a mixture of steam and a gas comprising oxygen, and the gasification is carried out at a temperature within the range of from 800 C. to 1300 C. under atmospheric to superatmospheric pressure.

10. A process as claimed in claim 9, wherein the reactive gas is a mixture of steam and oxygen alone.

11. A process as claimed in claim 10, wherein the gas that is passed upwardly through the separating zone is a part of the mixture of steam and oxygen.

12. A process as claimed in claim 9, wherein the gas that is passed upwardly through the separating zone consists of at least a part of the steam.

13. A process as claimed in claim 1, wherein the reactive gas is a gas comprising mainly of hydrogen, and the gasification is carried out at a temperature Within the range of from 700 C. to 1200 C. under a pressure of at least 5 atmospheres gauge.

14. Apparatus for the gasification of particulate solid ash-containing carbonaceous fuel, which comprises a re action vessel having in its upper part a region to accommodate a fluidised bed of the particulate material, two gas inlet means below the said region for supplying gas thereto, one of the said gas inlet means being disposed below the other at a distance suflicient to permit the formation of an ash-separating zone between the two inlet means, an upriser passage of which the lower end is above the upper gas inlet means and the upper end communicates with the region of the fluidised bed, a downcomer passage of which the upper end communicates with the said region and lower end communicates with the lower end of the upriser passage, an inlet for supplying the carbonaceous fuel to the said region, an outlet for product gas above the said region, an ash-collecting chamber below the lower gas inlet means, and an ash discharge outlet at the base of the ash'collecting chamber.

15. Apparatus as claimed in claim 14, wherein the said upriser passage is provided within a vertical open-ended tubular member of which the outer surface is spaced from the inner surface of the reaction vessel to form between these surfaces an annular downcomer passage.

References Cited UNlTED STATES PATENTS 1,866,399 7/1932 De Baufre 48-206 X 2,445,328 7/1948 Keith 48197 X 2,538,219 1/1951 Welty 48206 2,654,663 10/1953 Gorin 48197 2,868,631 1/1959 Woebcke 48206 3,004,839 10/1961 Tornquist 48197 MORRIS O. WOLK, Primary Examiner. J. SCOVRONEK, Assistant Examiner. 

14. APPARATUS FOR THE GASIFICATION OF PARTICULATE SOLID ASH-CONTAINING CARBONACEOUS FUEL, WHICH COMPRISESD A REACTION VESSEL HAVING IN ITS UPPER PART A REGION TO ACCOMMODATE A FLUIDISED BED OF THE PARTICULATE MATERIAL, TWO GAS INLET MEANS BELOW THE SAID REGION FOR SUPPLYING GAS THERETO, ONE OF THE SAID GAS INLET MEANS BEING DISPOSED BELOW THE OTHER AT A DISTANCE SUFFICIENT TO PERMIT THE FORMATION OF AN ASH-SEPARATING ZONE BETWEEN THE TWO INLET MEANS, AN UPRISER PASSAGE OF WHICH THE LOWER END IS ABOVE THE UPPER GAS INLET MEANS AND THE UPPER END COMMUNICATES WITH THE REGION OF THE FLUIDISED BED, A DOWNCOMER PASSAGE OF WHICH THE UPPER END COMMUNICATES WITH THE SAID REGION AND LOWER END COMMUNICATES WITH THE LOWER END OF THE UPPER PASSAGE, AN INLET FOR SUPPLYINGD THE CARBONACEOUS FUEL TO THE SAID REGION, AN OUTLET FOR PRODUCT GAS ABOVE THE SAID REGION, AN ASH-COLLECTING CHAMBER BELOW THE LOWER GAS INLET MEANS, AND AN ASH DISCHARGE OUTLET AT THE BASE OF THE ASH-COLLECTING CHAMBER. 